1. Field of the Invention
The present invention relates to a pressing member that is comprised by a sewing machine for sewing edge hems of two materials together which are overlapped with each other by a specified width.
2. Description of the Prior Art
Back-shoulder seaming of shirts or sewing from crotch to cuff of briefs and shorts is generally performed by the following process: an interlock chain-stitch sewing machine (flat seamer sewing machine) having a cylinder bed of narrow width is employed, and materials which are cut into specified shapes are vertically overlapped with each other at their respective edge hems by a specified width, are sent into a needle drop point and sewn together. At this time, in order to obtain a sewn article of good quality, it is important to keep the overlapping width of the materials that are sent into the needle drop point at a proper width that corresponds to a sewing width of the sewing machine.
Adjusting of the overlapping width of the materials is generally performed manually by an operator who performs the sewing at a position in front of a pressing member for pinch-pressing and holding materials between this member and a throat plate, but it presents a drawback in that this operation requires considerable skill. Accordingly, a sewing machine which does not require manual adjustment of the overlapping width has been conventionally proposed for practical use which is realized by the arrangement of a special pressing member comprising knives for cutting edge hems of materials even which are to be objects to be sewn together, as well as a guide means provided rearward of the knives for overlapping materials which have been cut even.
FIG. 1 is a perspective view of a proximity of a needle drop point of an interlock chain-stitch sewing machine which is equipped with such a conventional pressing member comprising the knives and guide means as above described.
As shown in the drawing, a pressing member 2, which is supported in a suspended manner at a tip portion of a sewing machine arm A, comprises a guide path 21 formed between a pair of presser feet 22, 23 which elastically contact a throat plate D on a sewing machine bed B with an opening in a front side. Materials KL, KR, which are to be objects to be sewn, are pinch-pressed at a proximity of their respective end portions between the presser feet 22, 23 and the throat plate D, sent into a needle drop point C by being applied with a feed in a direction indicated by a non-relief arrow in the drawing by the action of a feed dog (not shown) extruding over the throat plate D, and sewn together by needles 1, 1 . . . dropping onto the needle drop point C.
In performing this feeding, when the materials KL, KR are introduced into the guide path 21 in a condition in which they are put together with their end portions standing up, these upper edges reach a contact portion of an lower knife 24 and an upper knife 25 on halfway the guide path 21 and are cut even. The evenly cut end portions of the materials KL, KR are vertically overlapped, sent into the needle drop point C by the action of an upper guide 29 which is provided as to be protruding to the side of the guide path 21 from one presser foot 23 and of a lower guide 32 protruding to the side of the guide path 21 from the other presser foot 22 (see FIGS. 2B to 2D), and are made to be sewn by the needles 1, 1 . . . at a proper overlapping width.
FIGS. 2A to 2E are explanatory diagrams showing cutting and overlapping actions of materials KL, KR that are performed as above described, wherein FIG. 2A is a sectional view of a proximity of a front end portion of the pressing member 2, FIG. 2B of a cutting position of the lower knife 24 and upper knife 25, FIGS. 2C and 2D of a position somewhat rearward with respect to the cutting position, and FIG. 2E of a direction which is crossing a feeding position of the materials KL, KR at the needle drop point C.
As shown in these drawings, the upper guide 29 increases in extruding length to the guide path 21 in approaching the needle drop point C and also in thickness, and as shown in FIG. 2D, it is arranged in a manner such that it succeeds to the other presser foot 22 in a front side of the needle drop point C.
Further, as shown in FIG. 1, the lower guide 32 on the side of the presser foot 22 is arranged as follows: it is uniformly formed with a slide plate 30 attached on a lower surface of the presser foot 22 as to extend from the front end up to the rear end; it forms a specified gap with respect to the throat place D arranged downward; it increases in extruding length to the guide path 21 in approaching the needle drop point C, similarly to the upper guide 29; and, as shown in FIG. 2C, it is overlapped with an lower portion of the upper guide 29 as to form a specified gap in a region from somewhat rearward the cutting position of the lower knife 24 and upper knife 25 up to a position immediately in front of the needle drop point C, as shown in FIG. 2D.
As shown in FIG. 2A, materials KL, KR are overlapped at their respective edge hems by a portion of a specified width, and this overlapping portion is introduced into the guide path 21 in a condition in which this overlapping portion is standing up on the throat plate D. In order to make this introduction easy, there may also be used an auxiliary bar (shown by virtual lines) for maintaining the overlapping portion of the materials KL, KR in a standing-up condition.
The materials KL, KR introduced in this manner reach, as shown in FIG. 2B, at the contact position of the upper knife 24 and lower knife 25, and their upper hems are cut even. At this cutting position, the upper guide 29 and lower guide 32 present a specified extruding length to the guide path 21, and the cutting is performed in a condition in which an end surface of the upper guide 29 contacts the material KR on the right side and an end surface of the lower guide 32 contacts the material KL on the left side.
As shown in FIGS. 2C and 2D, the material KL of which upper hem has been cut even is pushed from the left side by the lower guide 32 which increases in extruding length in a direction of the guide path 21 and is made to fall onto the throat plate D arranged below. On the other hand, the material KR is pushed from the right side by the upper guide 29 which increases in extruding length in a direction of the guide path 21, guided between the upper guide 29 and the lower guide 32 which is overlapping with a lower portion of the upper guide 29, reaches a very end of the lower guide 32, overlaps with an upper portion of the material KL on the throat plate D, and is sent into the needle drop point C in this condition, whereupon the overlapping portion is sewn together by the needles 1, 1 . . . dropping onto needle drop point C, as shown in FIG. 2E.
By roughly overlapping materials KL, KR at their respective end portions and sending them into the pressing member 2 in a condition in which they are standing up on the throat place D in this manner, their end hems cut even by the lower knife 24 and upper knife 25, are vertically overlapped by the action of the upper guide 29 and lower guide 32, and are sent into the needle drop point C, whereby sewing of materials KL, KR at substantially constant overlapping widths can be realized without the necessity of manually adjusting the overlapping width.
However, while overlapping by the action of the upper guide 29 and lower guide 32 in the above manner can be smoothly performed in case materials KL, KR have a suitable thickness and elasticity, it may be that in case thin materials KL, KR which are quite flexible are to be sewn, the end hem of the material KR, which is guided by the action of the upper guide 29 into a position between this upper guide 29 and the lower guide 32, is bent between both guides 29, 32 as shown by the broken line in FIGS. 2C and 2D. When the materials are sent to the needle drop point C in this condition, it may happen that the surface material (material KR) is sewn to the back material (material KL) with a part of the end hem of the surface material being flapped to result in a sub-standard sewn article as shown in FIG. 3.